1. Field of the Invention
The invention relates generally to glassware forming machine of the rotating table type having a plurality of continuously rotating, circumferentially spaced forming units. More particularly, the invention relates to a press head adjustment mechanism for adjusting the pressing pressure of the plungers associated with the press head of each forming unit of the machine.
2. Description of the Prior Art
Glassware forming machines of the rotating table type are well known in the glassware manufacturing industry. One type of such machine is shown in U.S. Pat. No. 1,979,211 and is commonly referred to as the "Emhart H-28 Machine." This type of machine is a single table, continuous rotary motion machine having a plurality of individual forming units mounted for rotation about the axis of the machine. These machines have been available with different numbers of individual forming units, thus constituting, for example, a 6, 12 or 18 section machine. In such H-28 machines each individual forming unit produces one glassware article for each complete revolution or cycle of the machine and will therefore be referred to herein as H-28 single gob machines.
A significant improvement over the H-28 single gob machine is disclosed in U.S. Pat. No. 4,339,264 which describes an H-28 double gob machine where each individual forming unit produces two glassware articles for each complete cycle. This patent is hereby incorporated by reference in this disclosure in its entirety.
The prior art H-28 double gob machine has a ram spring pressure or pre-load adjustment associated with each plunger and a means for total pressing pressure adjustment with each plunger. Each of these adjustment mechanisms is similar to corresponding mechanisms in the H-28 single gob machine.
These adjustments are necessary to compensate for variations in gob weight or viscosity and are generally achieved by adjustment of the ram spring. When the plunger starts to contact the gob in the bottom of the blank mold, glass starts to flow around the plunger and to a certain extent resists its further downward motion. At some point the gob starts to lift the plunger thereby compressing the associated ram spring even though the press head continues to move downwardly. When the ram spring is compressing it forces the plunger into glass in the blank mold causing the molten glass to flow around the plunger. The force with which the plunger initially contacts the gob is determined by the ram spring pre-load adjustment.
Basically, the plunger pressing pressure is accomplished in prior art H-28 single and double gob machines through the use of nuts and stop nuts which alter the pre-load of the ram spring. Both sets of nuts and stop nuts are threadably engaged on opposite end of threaded rods parallel to and offset from the plunger stem. Because of the complexity of parts associated with the prior art H-28 double gob machine and its considerably greater height compared to the H-28 single gob machine it was found that the single gob ram spring adjustment method was inappropriate for the double gob configuration. Accordingly, one object of this invention is to provide a ram spring adjustment mechanism facilitating the operator's adjustment of ram spring forces. Another object of this invention is to provide a ram spring adjustment mechanism at a convenient, accessable height for the operator.